But since we are able to build 7 bases, almost one on each continent, I thought I would build 3 'main bases', in that they would have the basic production, alien facility, 2 storages, 1-2 labs, 2 living quarters, 1 team room, 1 large hangar and UFO hangar, and always 1 SAM plus the basics, to be able to respond to threats across the map without having to travel far, that way the Firebird is at less risk.
Minor quibbles here:
1) Alien Containment would only ever be needed at your research base. Since there are issues involved in transferring scientists, there is a built-in incentive to do all or most of your research at one location.
2) For Living Quarters i figure one per every two Workshops/Laboratories, plus an extra for your squad. more on this later
3) I'm mystified as to why the Team Room is already in the game, as it currently does nothing. There are plans for it but i feel it should have been left out until those plans become reality.
4) One building you didn't mention is the Hospital. It is not required, but very handy, to have one wherever your soldiers live.
5) I'm with Nevasith on the proliferation of squads. The more squads you have, the less experience each squad can accumulate. A single Firebird with two fuel tanks can reach anywhere in the world. The chance of it getting jumped by a Harvester are almost nil after you get all your radar sites working. Before that, it's going to be a crap shoot regardless. The only reason i can think of to use more than one squad is the tendency of the game to give you a Harvester to down right around the same time it gives you a new terror mission. In those cases, it is handy to have a 'B' squad to handle the Harvester while the 'A' squad deals with the terror mission. Even then, you would want to keep both squads at the same base. It makes logistics much simpler to only have to supply weapons and such to a single location, and you can exploit the way the game tracks these goods. Since these items are not kept by the soldier, but rather kept in base storage, you only need to buy/manufacture enough goods to supply one squad [with a reasonable amount of spares to cover battlefield losses].
And what about this base attack thing? Also, I would like to ask if the random UFO is a threat to my bases
As Nevasith has hinted, the game does not yet allow for Alien Invasion of your bases. Also there is no bombing, missile attacks, or anything like that. I believe the aliens will take 'interest' in a base when they fly directly over it. I don't know if the shooting down of that UFO stops 'the word' from getting around.